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Choosing a file format

Deciding how your images will be stored in your camera.


This road runner's image was captured and stored as a JPEG, the most common digital image format, probably, but not necessarily the best, depending on how the image will be used.
This road runner's image was captured and stored as a JPEG, the most common digital image format, probably, but not necessarily the best, depending on how the image will be used.

When you take a digital picture, your camera saves it in a specific format (or file type) - either as a JPEG, a TIFF or a RAW image.

All digital cameras (well, almost all) can save pictures in JPEG format, but not all of them can save pictures in the higher resolution TIFF and RAW formats. Some high-end digital SLR cameras employ the TIFF format, but it seems to be disappearing as fewer, if any, new cameras support it nowadays. Note that that doesn't mean TIFF is no longer useful as an image file format. This will become apparent as you read on, and learn about saving images as TIFF's for editing.

If your digital camera stores pictures only as JPEG's, the text in this section that discusses TIFF and RAW formats will not be of practical use to your immediate picture-taking. However, it will be of use in editing and saving your pictures on your computer, where you may choose to save an image as a TIFF file. And, it could prove to be of great value when you decide to upgrade to a new digital camera that may have the ability to store pictures in different formats.

Having an understanding of images saved as JPEG's and what can happen to them as you edit, save and re-save them should be of great interest to you, especially since it can affect the quality of your pictures.


WHAT DO THESE FORMAT NAMES, JPEG, TIFF & RAW, MEAN?

JPEG, pronounced "jay-peg," is an acronym for "Joint Photographic Experts Group." It describes an image file format standard in which the size of the file is reduced by compressing it, letting you fit more images onto memory cards than when using other formats. (The number of images is also affected by your choice of quality settings or resolution modes available in your camera. Go here and scroll down to Image resolution to find out about these settings, then later, you can also go here for more detailed information.) Some cameras will let you select the image compression rate (usually referred to as the "image quality") as normal, fine and super-fine. Higher compression rates produce smaller image files, with lower image quality. PEG also causes the image to be equally readable by many computer programs.

A "JPEG" image file name commonly carries the extension "jpg" - for example: "portrait-of-susan.jpg". But, it can also be identified by "jpe" and "jpeg" file extensions.

JPEG is the format to use when you want to fit a large number of images on your camera's media card, when you are photographing action shots using a high frame rate or when you don't want to spend a great deal of computer time editing your images in your image manipulation program, providing you are also willing to suffer a small trade-off in image quality. It is an ideal format to display your images on the internet or send them by email.

Compression of an image to JPEG format requires some image data to be discarded - known as "lossy" compression because information is lost.

Lossy compression is not as distressing as it sounds, though, since it is cleverly-done by removing non-essential or repeated data, for example, pixels that have the same value as those surrounding them. And, very important for you to know, you can control the amount of compression and therefore the amount of image information that will be lost, by choosing a compression level when you save the image. This is accomplished by the Quality setting you select on your camera and also by the Quality setting you choose when you save the image on your computer. In saving an image file as a JPEG, a suggested Quality setting is shown, ranging up to 12 (the highest quality setting). You can adjust this level, selecting a middle setting of 5 or 6 which provides a generally-satisfactory file size compression without noticeable quality loss (unless the same file is repeatedly saved at this quality level). Select a high setting of 10 to 12 for the highest quality, where the least reduction in image quality takes place. The file is compressed less and is therefore larger.

When you download a JPEG image file from your camera's memory card to your computer, and then open it in an image-editor, you can obviously make changes to it. Keep in mind, though, that when you save it again to incorporate the changes you made to it, it gets compressed again, and more image data is lost. The loss might not be noticeable until you have opened and re-saved it a number of times, especially if the picture was photographed at or is being saved at a low quality resolution setting, causing the image to gain artifacts that result in a loss of sharpness. The lower pictures on the right show how a JPEG with artifacts looks. It was multi-saved (11 times) at low resolution. You don't want this to happen to your pictures.

Each time you compress a JPEG image, the result is a lower-quality image. You cannot edit a JPEG image more than once or twice before it begins to degrade to an unusable condition. As a safeguard of your image's quality, you should, if possible, save an image that you plan to edit in a non-compressed TIFF or PSD file format.

A NOTE REGARDING THE JPEG 2000 FORMAT

JPEG 2000 is a fairly new image file format, described as an image coding system that uses state-of-the-art compression techniques based on wavelet technology, resulting in 20 percent smaller files that are of good quality but with some information discarded, unless the file is saved with the highest quality (100) selected, in which case, it is lossless. JPEG 2000 is aimed at not only improving compression performance over JPEG but also at improving features such as scalability and editability. There are no digital cameras that store images as JPEG 2000 files, and JPEG 2000 file name extensions include .jp2 and .jpx.

These pictures illustrate the
These pictures illustrate the "lossy" effect of repeatedly saving the same JPEG image, resulting in a picture that has gained artifacts (bottom), in which detail can become irreversibly blurred.

Although a TIFF image does not provide the compression of a JPEG, the TIFF image file has no quality loss when saving and re-saving it. But it does require high capacity memory cards for its large file sizes.
Although a TIFF image does not provide the compression of a JPEG, the TIFF image file has no quality loss when saving and re-saving it. But it does require high capacity memory cards for its large file sizes.

TIFF stands for "Tagged Image File Format," often touted as an uncompressed image format standard. (Uncompressed files are known as "non-lossy," "loss-free" or "lossless" files, since no image data is lost when saving the file.) TIFF image files can in fact be compressed using a range of compression ratios, including lossless LZW-compression, which is particularly suited to TIFF pictures that have large single-color areas. Opening a compressed TIFF file is slower than opening one that was not compressed, but not much slower. When left uncompressed or when compressed to a lesser degree, they are much larger than JPEG files, requiring more time for your camera to store an image on its memory card and requiring a much larger memory card to store the same number of images. If your camera permits you to save images as TIFF files, they will retain their quality even though they are compressed.

Created jointly by Microsoft and Aldus, TIFF's flexibility allowed it to be customized by programmers, resulting in numerous versions of TIFF. Some of these became so changed that they were incompatible with each other, so that certain TIFF files would not load into some image processing programs. That problem has been pretty much solved by modern software that easily converts any TIFF file to one that will load and can be manipulated.

Since a TIFF file can be opened in all image-processing programs, it is one of the most popular image formats for picture-editing, and is the main format for outputting to film or print. In fact, it is the best format for print production. Graphic artists and publications are accustomed to dealing with images in TIFF format. They are compatible with Mac or PC systems. TIFF image file names carry the extension "tif," or "tiff" as in a picture named "palomino.tif" or "palomino.tiff".

When you plan to edit a JPEG image in an image-manipulation application, save it first as a TIFF to avoid losing quality as you re-save it every now and then. You can change the file to a JPEG when you have finished working on it.


RAW is the format that contains the most information possible from a camera's sensor, in the form of raw data (computer code that defines the image's color information) that still needs to be processed further to make an image. Think of it as being similar to transparency film that contains raw (unretouched) image information just as it was photographed, unchanged by your camera as occurs when a JPEG or TIFF image is manipulated before being stored. Some folks like to consider a RAW image file as being similar to an unretouched negative which contains all of the picture information, exactly as it was photographed - with no compression (unless you select compression as an option, which can be done with some cameras that support RAW, such as Nikon's D2X digital camera, in which you can opt to save files as "Comp. NEF (Raw)" files, reducing file size by 40 to 50% with almost no effect on quality.) and no in-camera changes of any kind (truly raw data), providing them with the maximum flexibility for image manipulation. Of course, since there is normally no image compression when using the RAW format, the file size of pictures is much larger than JPEG, so your camera's memory card will be able to store fewer RAW images than JPEG images. You will need a high-capacity memory card if you are shooting in RAW format. (Digital cameras all shoot raw images, but most convert them to JPEG's with software inside the camera, and then discard the raw data.)

The RAW story is complicated since different camera manufacturers have created several versions of RAW. RAW does not mean one single format, but is in reality a name that describes all the proprietary RAW formats developed by every manufacturer for their cameras, like Nikon's "NEF" and Canon's "CRW" and "CR2" formats. This diversity of RAW versions means that you will need a specialized software program from your manufacturer for its camera's version of RAW, and / or third party software (like Adobe PhotoShop) that works with your camera's particular RAW format. Microsoft's RAW Image Thumbnailer and Viewer also provides the ability to view, organize, and print photos captured in RAW image formats from supported Canon and Nikon digital cameras.

Two advantages of saving your images in RAW format are:
(1) They have way more picture information, and:
(2) You can edit them as they were photographed, without any of the camera's settings (white balance, contrast, etc.) affecting them.

RAW files require significant computing power to manipulate, and need specialized software. Camera manufacturers may have their own software, sometimes not the best or easiest to use. Some image-editing applications, such as Adobe PhotoShop and PhotoShop Elements, are able to handle most, if not all, RAW format versions.

SHOULD I SHOOT IN RAW FORMAT?

The answer is probably and surprisingly "No", if you shoot a large number of pictures at a time and prefer not to spend a lot of time editing them. You are better off with JPEG or TIFF. It is arguable that JPEG image quality is virtually the same as RAW. Many photographers say they don't see quality differences between RAW and high quality JPEG formats, unless the files are super-enlarged. RAW files are inconvenient in that they take up a huge amount of storage space and require a long time to download, organize and edit.

If you take a modest number of pictures and enjoy manipulating your images for the ultimate final result, RAW could be for you. You may find you prefer the results from editing RAW images even though it is not as convenient, time-wise and storage-wise, as getting your picture right the first time - in the camera - and storing it as a JPEG, then saving it as a TIFF before editing it. The greatest advantage of RAW is the ability it gives you afterwards to correct for errors you made when shooting. If you capture the image properly in the camera, you will probably never need RAW.

The top picture shows a RAW image file ready for manipulation. The scene below it is a JPEG image file, edited for brightness, contrast and saturation.
The top picture shows a RAW image file ready for manipulation. The scene below it is a JPEG image file, edited for brightness, contrast and saturation.

Although shooting in RAW format may seem to be to your advantage, you will probably get more mileage out of taking digital pictures that you save in JPEG format.
Although shooting in RAW format may seem to be to your advantage, you will probably get more mileage out of taking digital pictures that you save in JPEG format.

JPEG, TIFF & RAW SUMMARIZED

You might want to think of these three key file formats in this simplified way:

  • JPEG - Image compressed to take up less hard drive space, but with some image loss;
  • TIFF - Uncompressed image, mainly - high detail, no image loss;
  • RAW - Maximum image information as photographed, giving you the greatest image-manipulation flexibility.

BUT, WHAT ABOUT ALL THE OTHER IMAGE FILE TYPES LIKE GIF, PSD AND OTHERS?

These formats and others are used by image-editing applications, not by digital cameras when storing images. You need only to be concerned with JPEG, TIFF and RAW when shooting pictures and saving them in your camera. Click here or on the "Image file types" link at the bottom of the page to learn about the more common ones you may come across.


HOW CAN YOU KNOW WHAT FORMAT IS IDEAL FOR YOUR PICTURE?

The format you choose when saving an image depends on what you intend to do with the picture. If it will only appear on the internet or in an email, JPEG is the format to choose. If you plan to edit your image, perhaps saving it several times as you edit it, you should probably save it first as a TIFF file before working on it, then save the final edited image as a JPEG to email it or upload it to the internet. But, if you plan to print it or have it published, then uncompressed TIFF or RAW will provide the highest image quality in the final result.

But, what happens if you intend to use the picture in, say an email, and there is a possibility that, later, it could be made into an enlargement or appear in a publication? Well, save it first as a TIFF or RAW file using your camera's settings, then, after downloading it, save a copy of the TIFF or RAW image as a JPEG for emailing. That provides you with a large TIFF or RAW back-up file as insurance in the event you do indeed need it later for a print. Note that many cameras, especially digital single lens reflex (dSLR) cameras, permit you to save the same image in both a JPEG and a RAW format, a useful option that gives you the best of both worlds.

IMAGE FILE FORMAT AND RESOLUTION WORK TOGETHER

The resolution setting controls of a digital camera are where you select the format in which to save your pictures. They are also, of course, where you choose the resolution for the pictures you are going to take. Click here or on the "Image resolution" link below to learn about selecting the proper resolution for your picture-taking.

The format you choose when saving an image depends on what you intend to do with the picture. If it will only appear on the internet or in an email, JPEG is the format to choose. But, if you plan to print it or have it published, then TIFF or RAW is best.
The format you choose when saving an image depends on what you intend to do with the picture. If it will only appear on the internet or in an email, JPEG is the format to choose. But, if you plan to print it or have it published, then TIFF or RAW is best.
Related topics...

Image file types

Image resolution